TJ Mechanical engineering and machinery 173 TK Electrical engineering. Electronics Nuclear engineering 143 TA Engineering (General). Civil engineering (General) 111 TP Chemical technology 106 L Education (General) 31 T Technology (General) 29 QD Chemistry 28 QA75 Electronic computers. Computer science 24 LB Theory and practice of education 19 Q Science (General) 13 QA Mathematics 12 QC Physics 11 TS Manufactures 10 Unspecified 9 TH Building construction 6 QH Natural history 5 HD28 Management. Industrial Management 3 LB1603 Secondary Education. High schools 3 NA Architecture 3 Q Science 3 QA76 Computer software 3 TD Environmental technology. Sanitary engineering 3 TL Motor vehicles. Aeronautics. Astronautics 3 TN Mining engineering. Metallurgy 3 GE Environmental Sciences 2 GV Recreation Leisure 2 H Social Sciences (General) 2 LB2300 Higher Education 2 QE Geology 2 T58.5-58.64 Information technology 2